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How Do Trees Clean the Air?

We have trees to thank for many things. They provide shade on sunny days, they offer food and shelter for many living things and they provide a livelihood for people all over the world. The main reason we should hug our trees, though, is that they help clean the air and improve air quality. This is why trees are often said to be the lungs of the planet.

A tree canopy and tall tree trunks seen from the ground below.
(Photo via Shutterstock)

How do they work as Earth's lungs? By breathing. That's right; trees breathe just like we do, but the process for trees is a reverse of how humans breathe. When we breathe, we inhale oxygen and exhale carbon dioxide. Trees, though, take in carbon dioxide and emit oxygen as part of the process of photosynthesis.

Trees don't just use carbon dioxide to make energy; they also store carbon dioxide in their fibers. This benefits us and the environment because it makes the air cleaner and limits the harmful effects of carbon dioxide.


Words to know

Livelihood: A way of securing necessities.

Noxious: Harmful, poisonous or unpleasant.

Ozone: An odorless, colorless gas that is part of the natural environment.

Particulate: Small particles of smoke, dust and other materials in the air.

Respiratory: Related to the organs used for respiration, or breathing.


Carbon dioxide is one of several things that cause air pollution, along with other noxious gases, ozone and particulate matter. Because trees store carbon dioxide, they reduce air pollution levels by removing some carbon dioxide from the atmosphere.

The ability to store carbon dioxide allows our trees and forests to function as carbon sinks, which is anything that absorbs more carbon than it emits into the atmosphere. Other carbon sinks include soil and our oceans. In the United States, trees and plants offset about 13% of total carbon dioxide emissions. A single mature tree can absorb more than 48 pounds of carbon dioxide in a year.

Carbon dioxide is one of several greenhouse gases, which are gases that trap heat in the atmosphere. Other greenhouse gases include methane, nitrous oxide and fluorinated gases. Carbon dioxide is the main greenhouse gas produced by human activity, primarily through transportation, electricity and industrial processes like manufacturing.

While trees are mostly known for helping prevent air pollution by removing carbon dioxide from the atmosphere, there is a second way they perform this role. They also remove particulate matter from the air. As particles of pollution circulate in the air, trees essentially catch them as they are deposited on the leaves and other surfaces of the tree.

Trees can also affect air pollution levels in indirect ways, especially in urban areas. The presence of trees in cities can lower air temperatures and reduce the energy being used to cool buildings, both of which help reduce air pollution.

All the ways in which trees help clean the air are a benefit to humans because air pollution affects our health and our enjoyment of the outdoors. Exposure to polluted air can have negative health effects, including an increased risk of respiratory infections, lung cancer and heart disease.

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